INORGANIC PIGMENTS WITH FOG-FREE GLOSS DISTRIBUTABLE IN LACQUER BINDERS

PIGMENTS INORGANIQUES A BRILLANCE UNIFORME DISPERSIBLES DANS DES LIANTS A LA LAQUE

English Abstract

A TRACT OF THE DISCLOSURE
An inorganic pigment exhibiting improved gloss
and distribution in lacquer binders, carrying a coating com-
prising a-SiOH-containing organosilicon compound and an
aklanolamine. Advantageously the alkanolamine comprises at
least one of triethanolamine, triisopropanolamine, diethanolamine,
diisopropanolamine and 2-amino-2-methyl-propanol-1, the organo-
silicon compound is of the formula
<IMG>
wherein n>3, R and R1 each independently is alkyl, cycloalkyl,
aryl, alkenyl or a group of the formula
<IMG>
herein m>1, the organosilicon compound having an OH:Si ratio
within the range of about 1:1 to 1:20, and the pigment comprises
T1O2 or a titanate carrying an inorganic coating, the organo-
silicon compound plus alkanolamine ranging from about 0.3 to
1% by weight of the organosilicon compound to alkanolamine
ranging from about 1:2 to 1:5.

Claims

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Claims:
1. An inorganic pigment with improved gloss and dis-
tribution in a lacquer binder having a coating of a SiOH-con-
taining organosilicon compound with more than three Si atoms
and an alkanolamine.
2. An inorganic pigment according to claim 1, wherein
the quantity of SiOH-containing organosilicon compound and
of alkanolamine is from about 0.1% to 3% based on the weight
of the pigment, and the ratio by weight of SiOH-containing
organosilicon compound to alkanolamine is from about 1:1 to
1:10.
3. An inorganic pigment according to claim 1, com-
prising TiO2 or a titanate.
4. An inorganic pigment according to claim 1, wherein
the organosilicon compound is of the formula
<IMG>
wherein n?3, R and R1 each independently is an alkyl, cycloalkyl,
aryl, alkenyl or a group of the formula
<IMG>
wherein m>1, the organosilicon compound having an OH:Si ratio
within the range of about 1:1 to 1:20.
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5. An inorganic pigment according to claim 1, wherein
organosilicon compound is of the formula
<IMG>
wherein n>3, R and R1 each independently is methyl, ethyl,
phenyl or a group of the formula
<IMG>
wherein m>1, the SiOH-containing organosilicon compound having
an OH:Si ratio within the range of about 1:1 to 1:20.
6. An inorganic pigment according to claim 1, wherein
the alkanolamine comprises at least one of triethanolamine,
diethanolamine, triisopropanolamine, diisopropanolamine and
2-amino-2-methyl-propanol.
7. An inorganic pigment according to claim 6, wherein-
the organosilicon compound is of the formula
<IMG>
wherein n>3, R and R1 each independently is methyl, ethyl,
phenyl or a group of the formula
<IMG>
wherein m>1, the SiOH-containing organosilicon compound having
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an OH:Si ratio within the range of about 1:2 to 1:10, and
the pigment comprises TiO2 or a titanate carrying an inorganic
coating, the organosilicon compound plus alkanolamine ranging
from about 0.3 to 1% by weight of the pigment and the ratio by
weight of the organosilicon compound to alkanolamine ranging
from about 1:2 to 1:5.
8. In the preparation of an inorganic pigment where-
in the pigment is produced by chemical reaction and is thereafter
micronized, the improvement which comprises mixing with the
pigment before or during micronization an SiOH-containing organo-
silicon compound with more than three Si atoms and an alkanol
amine.
9. A process according to claim 8, wherein the alkanol-
amine comprises at least one of triethanolamine, diethanolamine,
triisopropanolamine, diisopropanolamine and 2-amino-2-methyl-
propanol, the organosilicon compound is of the formula
<IMG>
wherein n>3, R and R1 each independently is methyl, ethyl,
phenyl or a group of the formula
<IMG>
wherein m>1, the SiOH-containing organosilicon compound having
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an OH:Si ratio within the range of about 1:2 to 1:10, and
the pigment comprises TiO2 or a titanate carrying an inorganic
coating, the organosilicon compound plus alkanolamine ranging
from about 0.3 to 1% by weight of the pigment and the ratio
by weight of the organosilicon compound to alkanolamine ranging
from about 1:2 to 1:5.
10. A polymeric material pigmented with a pigment
according to claim 1.
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Description

~ 3 ~3037
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Inorganic Pigments with improved gloss and good distribution
in Lacauer ~inders
The present invention relates to inorganic pi~ments
having improved gloss and distribution in lacquer binders
by means of treatment ~ith organic au.Yiliaries before or
during final mieronization.
~og-free high gloss eoatings and good subtlivisr;on in
lacquer binders are importan-t requirements of high quality
pigments. In adclition to ccr-tain o-thF3r properties such as
good resistanee to weathering and brightening capacity,
they constitnte important eriteria for assessing quality.
~here has been no lacl{ of attempts in the past to achieve
tlle above object. The charaeteristic procedure to achieve
this object in many patents is that of rendering tlle organo-
phobic surface of the pigment organ~pllilic by means of
suitable substances sueh as organic auxiliaries which are
added before or during the milling operation ~rhich concludes
the procluetion process. This milling of the pigments is
generally carried out in pin mills, ball mills or ring
roll mills bu-t e.Yeeptionally high quality pigments are
obtained by mieronizatiOn in fluid energy mills, e.g. using
air ,jets or steam jets. Numerous organic compounds are
l;nol~n as a,u~Yiliaries for modifying the sur-face of pigments.
Apart from polyols, alkene oYides, phello'ls~ long chain
fatty alcohols and fatty acid esters, to name but a few of
-tlle classes of compounds whieh may be usecl, it is also
kno~n to use organosilicon compounds. ~he object o~ ~Ising
these organosilicon compounds is to render the pigments or
fillers hydrophobie and to malse them more readily dispersi-
ble and capable of incorporation in syntlletic re~ins, In
German Offenlegungsschrift No. 2 012 017, -for e~Yample,
there is clescribed the treatmen-t of TiO2 ~v-ith sodium methyl
siliconate to improve its dispersibility in polystyrene.
lt is also customary to rendf3r pigments hydrophobie by
treating -them witll polysilo.Yanes, e.g. octamethylcyclotetra-
silo.Yane (British Pa,tent No. 959 211) to iml)rove their
incorporation in polyamicles, or to treat them ~ith silanes
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such as trialko.Yysilanes :Eor example, as descr:ibecl in
British Pa-tent No. 825 ~ 04. Such surface treatments are
not however, capable of producing pigments with excellent
fog-free gloss in lacquer bind~rs.
Organic treatment of pigments with alkanolamines is
also known. The use of trialkanolamines antl, diisopropano-
lamine, for example, have been described in US Patent No.
3 3~15 187 and ln German Patent No. 2 '~ 2 678, respectively.
In the process according to German OfIenlegungsschrift No.
1 792 022, tri.e~tllanolamine is brought into contact wi-th the
pigment surface in the course of so-ca]:Led double ste&m jet
milling. US Patent No. 2 737 ~160 is concerned wi-th the
milling of pigments with trial~anolamines in the presence of
~ finely dividecl fillers such as Aerosil. It is also known
15 -to use salts ol a]kanolamines with organic acids such as
lactic acid (German Patent No. 1 271 862) or benzoic acids
(US Patent No. 3 172 772).
The procedures mentioned above are either e~pensive
or technically complicated or else result in pigmen-ts
20 which, in spite of showing distinct improvements compared
with titanium dioxides which have not been organically
treated, do not satisfy the highest standards o:E quality
demanded with regard to gloss and fineness of subdivision
and dispersion. This applies partic~llar~ to pigments which
25 have been a~ter-treated with SiO2 or ~1~03.
It has now surprisingly been found that pigments with
improved gloss and good distribution in lacquer binders can
easily be obtained by treatment with organic auxiliaries
before their final micronization if a combination of alkano-
lamines with organic silicon compouncls containing SiOHgroups is used. The present invention provides inorganic
pigments with improved gloss and subdivision in lacquer
binders, having a coa-ting of organosilicon compounds con-
taining SiOH groups and having more thall threc Si atoms in
the mo]ecule and alkanolamines; and a l)rocess Lor the
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3 0 3 7
preparation thereof by coating the pigments with the above mentioned compounds
before or during their final micronization. Pigments which are particularly
suitable for this treatment are white pigments based on TiO2 or titanates,
including also those which have been subjected to an inorganic after-treatment.
The new pigments are particularly suitable for pigmenting polymer materials and
aqueous suspensions.
The pigments are brought into contact with about 0.1 to 4%,
preferably about 0.3 to 1% of the organic auxiliaries. It has been found
advantageous to use a proportion by weight of SiOH-containing organic silicon
compounds to alkanolamine within the range of about 1:1 to 1:10 particularly of
about 1:2 to 1:5. The preferred SiOH-containing organic silicon compounds are
characterized by an OH:Si ratio within the range of about 1:1 to 1:20, preferably
o:E about 1:2 to 1:10. Examples include linear and branched chain organic
silicon compounds corresponding to the following formula
R
HO - Si O - H
R' _ n
wherein n ~ 3, and R' may be the same as or different from R. R may be an alkyl
and/or a cycloalkyl and/or and aryl and/or an alkenyl group or a group
corresponding to the following formula
R
O Si O - - H
_ R' m
where m > 1.
Specific fractions of the hydrolyzates of, for example, the following
compounds are suitable: Dimethyldichlorosilane; dimethyldichlorosilane and
methyl trichlorosilane; dimethyldichlorosilane and silicon tetrachloride; vinyl
methyl dichlorosilane; vinyl methyl dichlorosilane and dimethyldichlorosilane,
cyclohexylmethyldichlorosilane and
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~ :1 63037
climethyldichlorosilane; and the like. Condensat.ion products of diphenylsilane-
diol are also suitable.
Particularly suitable compounds include, for example, linear poly-
methylsiloxanes end-blocked with SiOH groups having an average molecular weight
of about 490 and a viscosity of about 27 cP; also linear polyvinylmethylsiloxanes
end-blocked with SiOH groups having a ~MeSiViO) content of about 5%, a (SiOH)
content of about 18.2% and a viscosity of about 25.5 cP. Branched chain poly-
methylsiloxanes end-blocked with SiOH groups, an average molar weight of about
545 and a viscosity of about 110 cP as well as branched chain polyvinylmethyl-
siloxanes end-blocked with SiOH groups having a t~eSiViO) content of about 5% a
~SiOH) content of about 15.2% and a viscosity o~ about 96 cP are also suitable.
Common to all the above compounds is a certain ratio of OH groups to
Si atoms which in the process according to the present invention should be within
the range of from 1:1 to 1:20 if optimum pigment properties are to be obtained.
The alkanolamines used may be trialkanolamines, dialkanolamines
and/or monoalkanolamines. The following are particularly suitable: Triethanol-
amine~ diethanolamine, triisopropanolamine, diisopropanolamine, 2-amino-2-methyl-
l-propanol, 2-amino-2-hydroxy-methyl-1,3-propanediol, 2-dimethylaminoethanol,
2-ethylaminoethanol and the like. The organic auxiliaries are brought into
contact with the pigment in known manner, either before or during a final milling
operation. I~ is immlaterial whether they are mixed with the moist filter cake
obtained in the course of preparation of the pigment or with pastes or sludges of
the pigment before drying, whether they are directly added to the dry substance
in some suitable manner before the final milling, for example by spraying or else
whether, for example in the case of steam jet milling, they are directly added to
the steam before it is fed into the jet mill. The effectiveness of the compounds
used according to the present invention does not
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depend upon the sequence in which the components are
added. ~egardLess of whether mi~t~ires oI a:Lkanolamines
and organosilicon compounds are ac1ded or wh~t11er al~anol-
amines are ~dded first, followed by organosilicon compounds,
or vice-versa, the pigments obtained show considerable
improvement in gloss, fogging and granu~arites after they
have ~een micronized compared with products which have
only been treated with alkanoJamines alone or with organo-
silicon compounds alone.
. There is thus obviously a synergistic effect
between thes~ two substances, as can be seen from Table l
hereinai`ter.
The process of the present invention is suitable for
all inorganic ~hite and colored pigments. Particularly
15 advantageous results are obtained with white pigments based
on TiO2 or titanates or with iron o~ides. The pigments
may also have u21t1ergone an inorganic after-treat1nent
Pigmen-ts ~ith e~cellent gloss and good distribution are
obtained by the process according to the present invention.
TiO2 pigments of both the rutile or anatase form
obtaine~ by the sulphate process and thosc obtained by the
TiCl~ combustion process may be treated according to -the
prescnt invention. In the e~amples de-cri~ed in detail
below, ~iO2 pigmen-ts which have been treatecl with inorganic
25 compounds are surface treated with the organic auæiliaries
according to the present invention.
A furnace clinker, for e~ample is obtained after
several preliminary stages, and this clin1~er is milled and
graded. The line -fraction is subjected to an inorganic
aftertreatment, which may consist of the precipitation of
compounds such as Al(OH3), SiO2 or TiO2 011 the surface
thereof and may be rarried out by vario~ls methods in sus-
pension. The inorganically after-treated pigment slud~e is
Ireed from wa-ter in a rotary filter and ~as11ed. The residue
021 this ~irst rotaIy filter may be mi~ed with water and
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trans~erred -to a second rotary filter. The residue (II)
~rom this seconcl filter is also washed, and then driecl on
a drying belt or a sp-ray drier.
When the pigments have been dried, they are broken
down either by milling in a jet mill, e.g. an air jet mill,
or a steam jet mill~ or in a milling apparatus which has -
a conlpacting e~fect, such as a l~aymond mil:L9 a ball mill
or a pin mill. The organic auxiliaries acc,-rding to
the l~resent invention may be brought into contact with the
10 pigment at various stages before or during micronization.
For e~ample, they may be added to the second filter residue
(II) after it has been 1~ashed but before i-t is dried.
They may also be added to the dry pigmen-t substance, e g.
by spraying, immediately before it is micronized. Another
15 treatment method consists of adding the colllpounds used
according to the present invention to the steam or air fed
into the jet mill. The orgarlic au~iliaries according to
the present invention may be added advantageously as mix-
tures since this ensures the desired constant ratio of
20 alkanolamine to organosilicon compoullds.
According to another variation of the process of
the present invention, the orgal1osilicon compound containing
SiO~ groups is added to the filter residue (II) after it
has been washed and before it is dried, and the alkanol-
25 amine is added to the dry pigment by spraying before it ismilled, or else it is brought into contact 1~ith the pigment
together with -the steam or air.
The above means that the co1nbination of organic
auxiliaries may ~e added to the pigmcnt seI)arately at
30 various stages of the manufacturing process.
~ o test the pigment for gloss and distribution in
lacquer binders, it is dispersed ~y a dissolver. ~his dis-
persion is prodLIced in a highly viscous mi.Yture o~ binder
solution of 60~ alkyd resin (ricinene-moc1ified alk~d resin,
A 35 oil length 35; trac1e product Alkydal R 35 of ~AYER AG) in
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,Yyl ene under the following conditions:
Volumetric concentration of pigment in
m~terial to be groun~ (PVK): 37 6 %
Diam,ter of ~lissolver disc 3.5 cm - D
5 Diameter of container: 5.5 cm = 1.57 D
Distance of dissolver disc from bottom: 1.75 cm = 0.5 D
Height to which the container i~s filled
with material to be ground 3 5 cm - D
Péripheral speecl of dissolver disc: 11 m/s
10 Dispersion time: 5 minutes.
Samples are removed after a dispersion time of 5
minutes and lacquered to a P~of 15~ with the alkyd resin
~~~ and a melamine resin (Maprenal~MF 800, trade product of
Hoechst AG) so that the ratio of alkyd resin to melamine
resin is 77:23. The degree of fineness of the dispersion
is determined in the usual manner with a grindometer (DIN
53 203). The lacquers prepared in this way are then applied
to glass plates to form films 120 ,um when wet, and are
hardened at 120C for 30 minutes. TLte gloss is measure~
with a Gonio photomctcr at an angle oI 25 The height of
the peak at the ref~ection ma~imum is a moasure of the gloss
obtained ~hile the heig~t of the sca-tter curve 1 ne~t to
the reflection ma~imum is a measure of the gloss fog values.
A high gloss lacquer is characterized by high gloss
values and low gloss fog values.
The preparation of the pigments according to the
present invention is described below by way of e~ample.
r~De ~,/C
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A TiO2 pigmen-t having a ru-tile struc-ture and pre-
pared ~y ~he sulphate process was after--treated inor-
~anically with 3,~o~h SiO2 and 4% Ai2o3 and dried after
the usual washing and filtra-tion. The pigment was
sprayed with 0.1% by weight (based on dry pigment) of
an a,~-polysiioxanediol mixture having an average
molecular weight of 490 and a viscosity of 27cP and
O, 3% of trietllanolamine and then micronized in a jet mill
using superheated s-team. The dispersibili-ty, gloss and
gloss-f'og vallles are shown in Table I
'Comparison Example A~
This comparison Example A shows that a pigment
obtained wheli triethanolamine alone is used is qual-
itatively consiclerably inferior.
The rutile pigment described in Example 1 issprayed with O.~L,~o triethanolamine a:Eter drying and is
then micronized in a jet mill as described in Example 1.
The dispersing properties are shown in Table 1.
~ `
This comparison example shows that the use solely
of an organic Si compound containing SiOH groups also
results in a qualitatively inferior pigmen-t. The rutile
pigment describecl in Example 1 is dried and then sprayed
25 with 0. 4% of an a,w polysiloxanediol mi~ture having an
average molecular weight of 490 and a viscosity of 27 cP
and micronized. See ~able 1.
3 After drying, the rutile pigment as used in Example
1 is sprayed l~ith 0.17% of an a,w-po]ysiloxanediol mix-
ture having an avera~e molecular weigh-t Or ~90 an~ a
viscosity of 27 cP and 0.53% of triethanolamine and'
milled in a steam jet mill; see ~able 1.
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Example 3
The rutile pigment as used in Exampl.e l is dried
and then sprayed with 0.12% Of an a,w-polysiloxane diol
mixture having an average molecular weight o~ 1190 and 5 a viscosity Oï 27 CP and 0. 58% of trie-thanolamine and
milled in a s-team jet mill; see Table I .
~.
The washed filter cake of the rutile pigment as
used in Examp].e 1. is mixed, before drying, with 0.12,%
by weight (based on -the dry pigment) of a branched chain
~iOH-containing organosilicon compound having an average
overall.formula of TD6 56 and containing 14% Of SiOH
gro-ups. .After the pigment has been dried, it is sprayed
lS with 0.48% triethanolamine and mic~onized as described
in the previous example; see Table l.
The rutile pig~ent as used in Example l is sprayed
after drying with a mixture containing 0~12~o by weight
(basecl on -the dry pigment) of a polysi].oxanediol mixture
having an average molecular weight of 490 and a viscosity
of 27 cP and O . 48% by weight (based on dry pigment) of
2-amino-2-methyl~l-propanol and then milled in a ste~m
jet mill as described in Example l; see Tahle l.
Example 6
The rutile pigment as described in Example l does
not receive an organic after-treatment.
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Table 1 -10-
Example Organic Treatmerlt Gloss Fog Grind- Heg-
(%) (%) ometer man
value value
(,u )
1O. 1% Si-org.cpd. 8726 16 6.7
and
o . 3% triethanol-
amine
Compar-0.4,o triethanol- 7737 20 6.4
ison E~- amine
ample A
" B0.4% Si-org.cpd. 701l0 16 6~7
2 O.17% Si-org,cpd. 8524 16 6.7
and
O . 53% triethanol-
amine
3 0 .12% Si-org.cpd. 8721~ 16 6.7
and
0.580,h triethanol-
amine
4 0 .12% branch 8823 14 6.9
chained
Si_org.cpd.
and
0.48% triethanol-
amine
0.12,h Si-org.cpd. 8625 14 6.9
and
O . 48% 2-amino-2-
methyl-l-
propanol
6 None 1~9~100 38 40
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It will be appreciated that the instant speci-
fication and examples are set forth by way of illustra
tion and not limitatlon, and that various modifications
and changes may be made without departing from the spi-
rit and scope of the present invention.
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